![Yuma Sunset](/sites/desertagsolutions.org/files/styles/topic_card/public/2024-03/TyCook4-final_permissio%20nfor%20YCEDA%20website%20only%5B71%5D.jpg?h=186734e1&itok=xv5HN_Rd)
Increasing Irrigation Efficiency
Water Use and Management
Updated Crop Evapotranspiration (ET) & Salinity Management
Boston and Leaf Lettuce
Two other types of lettuce produced in the Lower Colorado River region near Yuma, Arizona, are Boston and leaf lettuce. Reporting on acreage and economic value does not distinguish between lettuce types, but the land area cropped to these lettuce types is much smaller than iceberg and romaine lettuce.
Like the other lettuce types, stands are often established by solid set sprinklers and receive furrow irrigation for all subsequent irrigation. However, in some situations these two lettuce types are irrigated by sprinklers all season. These two lettuce types have similar growth periods and water use characteristics and our presentation for these two crops were combined.
Using eddy covariance (Figure 1), we have measured seasonal ETc from 184.5 to 212.5 mm (7.3 to 8.4 acre-inches). Like the other cool season crops days from first irrigation to harvest vary, growth and water use are more accurately tracked using growing degree days and satellite imagery. The calculated crop coefficients by growing period are shown in Table 1. As for most cool season vegetable crops at Yuma, irrigation efficiencies are high in-season and salinity increases. An off-season pre-irrigation is usually required to restore salt balance.
Table 1
Boston and leaf lettuce heat units, NDVI, and Kc values classified by FAO-56 growth stages.
Stage | GDD (C-Day) | GDD (F-Day) | NDVI | Kc |
---|---|---|---|---|
INI | 0.089 | 0.52 | ||
INI/DEV | 476.5 | 889.7 | 0.155 | |
DEV/MID | 880.6 | 1617.1 | 0.695 | 0.60 |
MID/END | 1064.1 | 1947.5 | 0.695 | |
END | 1189.0 | 2172.2 | 0.408 |
![Figure 1. Eddy Covariance system in a furrow irrigated leaf lettuce field in the Wellton Mohawk Irrigation and Drainage District.](/sites/desertagsolutions.org/files/styles/az_large/public/2024-06/lettuceBRFig1.png?itok=TTI6FlXZ)
Figure 1
Eddy Covariance system in a furrow irrigated leaf lettuce field in the Wellton Mohawk Irrigation and Drainage District.
![Figure 2. Eddy covariance system in Boston field within the Bard Water District irrigation by sprinklers all season.](/sites/desertagsolutions.org/files/styles/az_large/public/2024-06/lettuceBRFig2.png?itok=jZDuSeIZ)
Figure 2
Eddy covariance system in Boston field within the Bard Water District irrigation by sprinklers all season.
![Figure 3. Salinity increases over leaf lettuce production period in Yuma County Water Users Association.](/sites/desertagsolutions.org/files/styles/az_large/public/2024-06/lettuceBRFig3.png?itok=iIINqNQo)
Figure 3
Salinity increases over leaf lettuce production period in Yuma County Water Users Association.